206 results found
Davies E, Forsyth R, Good S, et al., 2020, On the radial and longitudinal variation of a magnetic cloud: ACE, wind, ARTEMIS and Juno observations, Solar Physics: a journal for solar and solar-stellar research and the study of solar terrestrial physics, Vol: 295, ISSN: 0038-0938
We present observations of the same magnetic cloud made near Earth by the Advance Composition Explorer (ACE), Wind, and the Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon’s Interaction with the Sun (ARTEMIS) mission comprising the Time History of Events and Macroscale Interactions during Substorms (THEMIS) B and THEMIS C spacecraft, and later by Juno at a distance of 1.2 AU. The spacecraft were close to radial alignment throughout the event, with a longitudinal separation of 3.6∘ between Juno and the spacecraft near Earth. The magnetic cloud likely originated from a filament eruption on 22 October 2011 at 00:05 UT, and caused a strong geomagnetic storm at Earth commencing on 24 October. Observations of the magnetic cloud at each spacecraft have been analysed using minimum variance analysis and two flux rope fitting models, Lundquist and Gold–Hoyle, to give the orientation of the flux rope axis. We explore the effect different trailing edge boundaries have on the results of each analysis method, and find a clear difference between the orientations of the flux rope axis at the near-Earth spacecraft and Juno, independent of the analysis method. The axial magnetic field strength and the radial width of the flux rope are calculated using both observations and fitting parameters and their relationship with heliocentric distance is investigated. Differences in results between the near-Earth spacecraft and Juno are attributed not only to the radial separation, but to the small longitudinal separation which resulted in a surprisingly large difference in the in situ observations between the spacecraft. This case study demonstrates the utility of Juno cruise data as a new opportunity to study magnetic clouds beyond 1 AU, and the need for caution in future radial alignment studies.
Good SW, Kilpua EKJ, LaMoury AT, et al., 2019, Self‐similarity of ICME flux ropes: Observations by radially aligned spacecraft in the inner Heliosphere, Journal of Geophysical Research: Space Physics, Vol: 124, Pages: 4960-4982, ISSN: 2169-9380
Interplanetary coronal mass ejections (ICMEs) are a significant feature of the heliospheric environment and the primary cause of adverse space weather at the Earth. ICME propagation and the evolution of ICME magnetic field structure during propagation are still not fully understood. We analyze the magnetic field structures of 18 ICME magnetic flux ropes observed by radially aligned spacecraft in the inner heliosphere. Similarity in the underlying flux rope structures is determined through the application of a simple technique that maps the magnetic field profile from one spacecraft to the other. In many cases, the flux ropes show very strong underlying similarities at the different spacecraft. The mapping technique reveals similarities that are not readily apparent in the unmapped data and is a useful tool when determining whether magnetic field time series observed at different spacecraft are associated with the same ICME. Lundquist fitting has been applied to the flux ropes, and the rope orientations have been determined; macroscale differences in the profiles at the aligned spacecraft may be ascribed to differences in flux rope orientation. Assuming that the same region of the ICME was observed by the aligned spacecraft in each case, the fitting indicates some weak tendency for the rope axes to reduce in inclination relative to the solar equatorial plane and to align with the solar east‐west direction with heliocentric distance.Plain Language SummaryCoronal mass ejections (CMEs) are large eruptions of magnetic field and plasma from the Sun. When they arrive at the Earth, these eruptions can cause significant damage to ground and orbital infrastructure; forecasting this “space weather” impact of CMEs at the Earth remains a difficult task. The impact of individual CMEs is largely dependent on their magnetic field configurations, and an important aspect of space weather forecasting is understanding how CME field configuration changes with distance from t
Good SW, Forsyth RJ, Eastwood JP, et al., 2018, Correlation of ICME magnetic fields at radially aligned spacecraft, Solar Physics, Vol: 293, ISSN: 0038-0938
The magnetic field structures of two interplanetary coronal mass ejections (ICMEs), each observed by a pair of spacecraft close to radial alignment, have been analysed. The ICMEs were observed in situ by MESSENGER and STEREO-B in November 2010 and November 2011, while the spacecraft were separated by more than 0.6 AU in heliocentric distance, less than 4° in heliographic longitude, and less than 7° in heliographic latitude. Both ICMEs took approximately two days to travel between the spacecraft. The ICME magnetic field profiles observed at MESSENGER have been mapped to the heliocentric distance of STEREO-B and compared directly to the profiles observed by STEREO-B. Figures that result from this mapping allow for easy qualitative assessment of similarity in the profiles. Macroscale features in the profiles that varied on timescales of one hour, and which corresponded to the underlying flux rope structure of the ICMEs, were well correlated in the solar east–west and north–south directed components, with Pearson’s correlation coefficients of approximately 0.85 and 0.95, respectively; microscale features with timescales of one minute were uncorrelated. Overall correlation values in the profiles of one ICME were increased when an apparent change in the flux rope axis direction between the observing spacecraft was taken into account. The high degree of similarity seen in the magnetic field profiles may be interpreted in two ways. If the spacecraft sampled the same region of each ICME (i.e. if the spacecraft angular separations are neglected), the similarity indicates that there was little evolution in the underlying structure of the sampled region during propagation. Alternatively, if the spacecraft observed different, nearby regions within the ICMEs, it indicates that there was spatial homogeneity across those different regions. The field structure similarity observed in these ICMEs points to the value of placing in situ space weather monitors w
Moestl C, Isavnin A, Boakes PD, et al., 2017, Modeling observations of solar coronal mass ejections with heliospheric imagers verified with the Heliophysics System Observatory, Space Weather-the International Journal of Research and Applications, Vol: 15, Pages: 955-970, ISSN: 1539-4956
We present an advance toward accurately predicting the arrivals of coronal mass ejections (CMEs) at the terrestrial planets, including Earth. For the first time, we are able to assess a CME prediction model using data over two thirds of a solar cycle of observations with the Heliophysics System Observatory. We validate modeling results of 1337 CMEs observed with the Solar Terrestrial Relations Observatory (STEREO) heliospheric imagers (HI) (science data) from 8 years of observations by five in situ observing spacecraft. We use the self-similar expansion model for CME fronts assuming 60° longitudinal width, constant speed, and constant propagation direction. With these assumptions we find that 23%–35% of all CMEs that were predicted to hit a certain spacecraft lead to clear in situ signatures, so that for one correct prediction, two to three false alarms would have been issued. In addition, we find that the prediction accuracy does not degrade with the HI longitudinal separation from Earth. Predicted arrival times are on average within 2.6 ± 16.6 h difference of the in situ arrival time, similar to analytical and numerical modeling, and a true skill statistic of 0.21. We also discuss various factors that may improve the accuracy of space weather forecasting using wide-angle heliospheric imager observations. These results form a first-order approximated baseline of the prediction accuracy that is possible with HI and other methods used for data by an operational space weather mission at the Sun-Earth L5 point.
Good SW, Forsyth RJ, 2016, Interplanetary coronal mass ejections observed by MESSENGER and Venus Express, Solar Physics, Vol: 291, Pages: 239-263, ISSN: 1573-093X
Interplanetary coronal mass ejections (ICMEs) observed by the MESSENGER and Venus Express spacecraft have been catalogued and analysed. The ICMEs were identified by a relatively smooth rotation of the magnetic field direction consistent with a flux rope structure, coinciding with a relatively enhanced magnetic field strength. A total of 35 ICMEs were found in the surveyed MESSENGER data (primarily from March 2007 to April 2012), and 84 ICMEs in the surveyed Venus Express data (from May 2006 to December 2013). The ICME flux rope configurations have been determined. Ropes with northward leading edges were about four times more common than ropes with southward leading edges, in agreement with a previously established solar cycle dependence. Ropes with low inclinations to the solar equatorial plane were about four times more common than ropes with high inclinations, possibly an observational effect. Left- and right-handed ropes were observed in almost equal numbers. In addition, data from MESSENGER, Venus Express, STEREO-A, STEREO-B and ACE were examined for multipoint signatures of the catalogued ICMEs. For spacecraft separations below 15° in heliocentric longitude, the second spacecraft observed the ICME flux rope in 82 % of cases; this percentage dropped to 49 % for separations between 15 and 30°, to 18 % for separations between 30 and 45°, and to 12 % for separations between 45 and 60°. As the spacecraft separation increased, it became increasingly likely that only the sheath and not the flux rope of the ICME was observed, in agreement with the notion that ICME flux ropes are smaller in longitudinal extent than the shocks or discontinuities that they often drive. Furthermore, this study has identified 23 ICMEs observed by pairs of spacecraft close to radial alignment. A detailed analysis of these events could lead to a better understanding of how ICMEs evolve during propagation.
Good SW, Forsyth RJ, Raines JM, et al., 2015, Radial Evolution of a Magnetic Cloud: MESSENGER, STEREO, and Venus Express Observations, Astrophysical Journal, Vol: 807, Pages: 177-189, ISSN: 1538-4357
The Solar Orbiter and Solar Probe Plus missions will provide observations of magnetic clouds closer to the Sunthan ever before, and it will be good preparation for these missions to make full use of the most recent in situ datasets from the inner heliosphere—namely, those provided by MErcury Surface, Space ENvironment, GEochemistry,and Ranging (MESSENGER) and Venus Express—for magnetic cloud studies. We present observations of thesame magnetic cloud made by MESSENGER at Mercury and later by Solar TErrestrial RElations Observatory-B(STEREO-B), while the spacecraft were radially aligned in 2011 November. Few such radial observations ofmagnetic clouds have been previously reported. Estimates of the solar wind speed at MESSENGER are alsopresented, calculated through the application of a previously established technique. The cloudʼs flux rope has beenanalyzed using force-free fitting; the rope diameter increased from 0.18 to 0.41 AU (corresponding to an rH0.94dependence on heliocentric distance, rH), and the axial magnetic field strength dropped from 46.0 to 8.7 nT (an -rH1.84 dependence) between the spacecraft, clear indications of an expanding structure. The axial magnetic flux was∼0.50 nT AU2 at both spacecraft, suggesting that the rope underwent no significant erosion through magneticreconnection between MESSENGER and STEREO-B. Further, we estimate the change in the cloudʼs angular widthby assuming helicity conservation. It has also been found that the rope axis rotated by 30° between the spacecraftto lie close to the solar equatorial plane at STEREO-B. Such a rotation, if it is a common feature of coronal massejection propagation, would have important implications for space weather forecasting.
Owens MJ, Forsyth RJ, 2013, The Heliospheric Magnetic Field, LIVING REVIEWS IN SOLAR PHYSICS, Vol: 10, ISSN: 2367-3648
Moestl C, Farrugia CJ, Kilpua EKJ, et al., 2012, MULTI-POINT SHOCK AND FLUX ROPE ANALYSIS OF MULTIPLE INTERPLANETARY CORONAL MASS EJECTIONS AROUND 2010 AUGUST 1 IN THE INNER HELIOSPHERE, ASTROPHYSICAL JOURNAL, Vol: 758, ISSN: 0004-637X
Harrison RA, Davies JA, Moestl C, et al., 2012, AN ANALYSIS OF THE ORIGIN AND PROPAGATION OF THE MULTIPLE CORONAL MASS EJECTIONS OF 2010 AUGUST 1, ASTROPHYSICAL JOURNAL, Vol: 750, ISSN: 0004-637X
Temmer M, Vrsnak B, Rollett T, et al., 2012, CHARACTERISTICS OF KINEMATICS OF A CORONAL MASS EJECTION DURING THE 2010 AUGUST 1 CME-CME INTERACTION EVENT, ASTROPHYSICAL JOURNAL, Vol: 749, ISSN: 0004-637X
Savani NP, Owens MJ, Rouillard AP, et al., 2011, EVOLUTION OF CORONAL MASS EJECTION MORPHOLOGY WITH INCREASING HELIOCENTRIC DISTANCE. II. IN SITU OBSERVATIONS, ASTROPHYSICAL JOURNAL, Vol: 732, ISSN: 0004-637X
Savani NP, Owens MJ, Rouillard AP, et al., 2011, EVOLUTION OF CORONAL MASS EJECTION MORPHOLOGY WITH INCREASING HELIOCENTRIC DISTANCE. I. GEOMETRICAL ANALYSIS, ASTROPHYSICAL JOURNAL, Vol: 731, ISSN: 0004-637X
Rouillard AP, Lavraud B, Sheeley NR, et al., 2010, WHITE LIGHT AND IN SITU COMPARISON OF A FORMING MERGED INTERACTION REGION, ASTROPHYSICAL JOURNAL, Vol: 719, Pages: 1385-1392, ISSN: 0004-637X
Savani NP, Owens MJ, Rouillard AP, et al., 2010, OBSERVATIONAL EVIDENCE OF A CORONAL MASS EJECTION DISTORTION DIRECTLY ATTRIBUTABLE TO A STRUCTURED SOLAR WIND, ASTROPHYSICAL JOURNAL LETTERS, Vol: 714, Pages: L128-L132, ISSN: 2041-8205
Rouillard AP, Lavraud B, Davies JA, et al., 2010, Intermittent release of transients in the slow solar wind: 2. In situ evidence, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 115, ISSN: 2169-9380
Rouillard AP, Davies JA, Lavraud B, et al., 2010, Intermittent release of transients in the slow solar wind: 1. Remote sensing observations, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 115, ISSN: 2169-9380
Jones GH, Forsyth RJ, Coates AJ, 2010, The Structure of Comets' Induced Magnetotails: Remote and in situ Observations, PICKUP IONS THROUGHOUT THE HELIOSPHERE AND BEYOND, Publisher: AMER INST PHYSICS, Pages: 225-230, ISSN: 0094-243X
Malandraki OE, Marsden RG, Lario D, et al., 2009, ENERGETIC PARTICLE OBSERVATIONS AND PROPAGATION IN THE THREE-DIMENSIONAL HELIOSPHERE DURING THE 2006 DECEMBER EVENTS, ASTROPHYSICAL JOURNAL, Vol: 704, Pages: 469-476, ISSN: 0004-637X
Rouillard AP, Davies JA, Forsyth RJ, et al., 2009, A solar storm observed from the Sun to Venus using the STEREO, Venus Express, and MESSENGER spacecraft, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 114, ISSN: 2169-9380
Rouillard AP, Savani NP, Davies JA, et al., 2009, A Multispacecraft Analysis of a Small-Scale Transient Entrained by Solar Wind Streams, SOLAR PHYSICS, Vol: 256, Pages: 307-326, ISSN: 0038-0938
Ebert RW, McComas DJ, Elliott HA, et al., 2009, Bulk properties of the slow and fast solar wind and interplanetary coronal mass ejections measured by Ulysses: Three polar orbits of observations, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 114, ISSN: 2169-9380
Savani NP, Rouillard AP, Davies JA, et al., 2009, The radial width of a Coronal Mass Ejection between 0.1 and 0.4 AU estimated from the Heliospheric Imager on STEREO, ANNALES GEOPHYSICAE, Vol: 27, Pages: 4349-4358, ISSN: 0992-7689
Wimmer-Schweingruber RF, McNutt R, Fahr H, et al., 2009, The interstellar heliopause probe: Heliospheric boundary explorer mission to the interstellar medium, Pages: 17-24, ISSN: 0167-9295
The Sun, driving a supersonic solar wind, cuts out of the local interstellar medium a giant plasma bubble, the heliosphere. ESA, jointly with NASA, has had an important role in the development of our current understanding of the Suns' immediate neighborhood. Ulysses is the only spacecraft exploring the third, out-of-ecliptic dimension, while SOHO has allowed us to better understand the influence of the Sun and to image the glow of interstellar matter in the heliosphere. Voyager 1 has recently encountered the innermost boundary of this plasma bubble, the termination shock, and is returning exciting yet puzzling data of this remote region. The next logical step is to leave the heliosphere and to thereby map out in unprecedented detail the structure of the outer heliosphere and its boundaries, the termination shock, the heliosheath, the heliopause, and, after leaving the heliosphere, to discover the true nature of the hydrogen wall, the bow shock, and the local interstellar medium beyond. This will greatly advance our understanding of the heliosphere that is the best-known example for astrospheres as found around other stars. Thus, IHP/HEX will allow us to discover, explore, and understand fundamental astrophysical processes in the largest accessible plasma laboratory, the heliosphere. © Springer Science+Business Media B.V. 2009.
Jackman CM, Forsyth RJ, Dougherty MK, 2008, The overall configuration of the interplanetary magnetic field upstream of Saturn as revealed by Cassini observations, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 113, ISSN: 0148-0227
Rouillard AP, Davies JA, Forsyth RJ, et al., 2008, First imaging of corotating interaction regions using the STEREO spacecraft, GEOPHYSICAL RESEARCH LETTERS, Vol: 35, ISSN: 0094-8276
Malandraki OE, Marsden RG, Tranquille C, et al., 2008, Energetic particle measurements from the Ulysses/COSPIN/LET instrument obtained during the August/September 2005 events, ANNALES GEOPHYSICAE, Vol: 26, Pages: 1029-1037, ISSN: 0992-7689
Malandraki OE, Marsden RG, Tranquille C, et al., 2007, Energetic particle observations by Ulysses during the declining phase of solar cycle 23, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 112, ISSN: 2169-9380
Malandraki OE, Marsden RG, Lario D, et al., 2007, Particle observations and propagation in the three-dimensional Heliosphere, Pages: 151-154
Ulysses, the first spacecraft ever to fly over the poles of the Sun, plays a central role in the Heliospheric Network, the international fleet of spacecraft to explore the Sun and Heliosphere. In November 2006, Ulysses began its passage over the Sun's south pole for the third time. Although like during the first polar passes in 1994/1995 the Sun is again close to its activity minimum, an unexpected rise of solar activity occurred in December 2006. Active Region 10930 produced a series of major solar flares with the strongest one (X9.0) recorded on December 5 after it rotated into view on the solar east limb. We present energetic particle observations by Ulysses located at >70 deg south heliolatitude during this period and discuss their implications for particle propagation to solar polar regions. The observed events are also compared with previous Ulysses high latitude measurements obtained close to solar maximum. Furthermore, comparisons with data acquired from ACE - another spacecraft of the Heliospheric Network - near the ecliptic plane are discussed.
Carr CM, Horbury TS, Balogh A, et al., 2006, A magnetometer for the Solar Orbiter Mission, ISSN: 0379-6566
The magnetometer is a key instrument to the Solar Orbiter mission. The magnetic field is a fundamental parameter in any plasma: a precise and accurate measurement of the field is essential for understanding almost all aspects of plasma dynamics such as shocks and stream-stream interactions. Many of Solar Orbiter's mission goals are focussed around the links between the Sun and space. A combination of in situ measurements by the magnetometer, remote measurements of solar magnetic fields and global modelling is required to determine this link and hence how the Sun affects interplanetary space. The magnetic field is typically one of the most precisely measured plasma parameters and is therefore the most commonly used measurement for studies of waves, turbulence and other small scale phenomena. It is also related to the coronal magnetic field which cannot be measured directly. Accurate knowledge of the magnetic field is essential for the calculation of fundamental plasma parameters such as the plasma beta, Alfven speed and gyroperiod. We describe here the objectives and context of magnetic field measurements on Solar Orbiter and an instrument that fulfils those objectives as defined by the scientific requirements for the mission.
Krueger H, Graps AL, Hamilton DP, et al., 2006, Ulysses jovian latitude scan of high-velocity dust streams originating from the jovian system, PLANETARY AND SPACE SCIENCE, Vol: 54, Pages: 919-931, ISSN: 0032-0633
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