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ICME Evolution in the Inner Heliosphere
Luhmann, J. G.; Jian, L. K.; Gopalswamy, N. +1 more
ICMEs (interplanetary coronal mass ejections), the heliospheric counterparts of what is observed with coronagraphs at the Sun as CMEs, have been the subject of intense interest since their close association with geomagnetic storms was established in the 1980s. These major interplanetary plasma and magnetic field transients, often preceded and acco…
Peculiar Solar Sources and Geospace Disturbances on 20-26 August 2018
Chertok, I. M.; Belov, A. V.; Abunina, M. A. +1 more
On the approach to minimum of Solar Cycle 24, on 26 August 2018, an unexpectedly strong geomagnetic storm (GMS) suddenly occurred. Its Dst index reached −174 nT, that is, the third most intense storm of the cycle. The analysis showed that it was initiated by a two-step long filament eruption, which occurred on 20 August in the central s…
On the Radial and Longitudinal Variation of a Magnetic Cloud: ACE, Wind, ARTEMIS and Juno Observations
Davies, Emma E.; Kilpua, Emilia K. J.; Forsyth, Robert J. +1 more
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 sp…
Evolution of Coronal Mass Ejections and the Corresponding Forbush Decreases: Modeling vs. Multi-Spacecraft Observations
Dumbović, Mateja; Temmer, Manuela; Veronig, Astrid +9 more
One of the very common in situ signatures of interplanetary coronal mass ejections (ICMEs), as well as other interplanetary transients, are Forbush decreases (FDs), i.e. short-term reductions in the galactic cosmic ray (GCR) flux. A two-step FD is often regarded as a textbook example, which presumably owes its specific morphology to the fact that …
Timing Terminators: Forecasting Sunspot Cycle 25 Onset
McIntosh, Scott W.; Leamon, Robert J.; Chapman, Sandra C. +1 more
Recent research has demonstrated the existence of a new type of solar event, the "terminator." Unlike the Sun's signature events, flares and coronal mass ejections, the terminator most likely originates in the solar interior, at or near the tachocline. The terminator signals the end of a magnetic activity cycle at the Sun's equator and the start o…
The STIX Aspect System (SAS): The Optical Aspect System of the Spectrometer/Telescope for Imaging X-Rays (STIX) on Solar Orbiter
Strassmeier, K. G.; Krucker, S.; Mann, G. +28 more
The Spectrometer/Telescope for Imaging X-rays (STIX) is a remote sensing instrument on Solar Orbiter that observes the hard X-ray bremsstrahlung emission of solar flares. This paper describes the STIX Aspect System (SAS), a subunit that measures the pointing of STIX relative to the Sun with a precision of ±4″, which is required to accur…
Coronal Photopolarimetry with the LASCO-C2 Coronagraph over 24 Years [1996 - 2019]
Lamy, Philippe; Gilardy, Hugo; Llebaria, Antoine +3 more
We present an in-depth characterization of the polarimetric channel of the Large-Angle Spectrometric COronagraph/LASCO-C2 onboard the Solar and Heliospheric Observatory (SOHO). The polarimetric analysis of the white-light images makes use of polarized sequences composed of three images obtained though three polarizers oriented at +60∘, …
Analysis of Large Deflections of Prominence-CME Events during the Rising Phase of Solar Cycle 24
Stenborg, Guillermo; West, Matthew J.; Mierla, Marilena +7 more
The analysis of the deflection of coronal mass ejection (CME) events plays an important role in the improvement of the forecasting of their geo-effectiveness. Motivated by the scarcity of comprehensive studies of CME events with a focus on the governing conditions that drive deflections during their early stages, we performed an extensive analysis…
Trajectory Determination for Coronal Ejecta Observed by WISPR/Parker Solar Probe
Qiu, J.; Howard, R. A.; Vourlidas, A. +3 more
The Wide-field Imager for Solar Probe (WISPR) onboard the Parker Solar Probe (PSP), observing in white light, has a fixed angular field of view, extending from 13.5∘ to 108∘ from the Sun and approximately 50∘ in the transverse direction. Because of the highly elliptical orbit of PSP, the physical extent of the imag…
Coronal Electron Density Fluctuations Inferred from Akatsuki Spacecraft Radio Observations
Imamura, T.; Song, P.; Ando, H. +6 more
Trans-coronal radio observations were taken during the 2011 observing campaign of the Akatsuki spacecraft through superior conjunction. The observed X-band (8.4 GHz) signals exhibit frequency fluctuations (FF) that are produced by temporal variations in electron density along the radio ray path. A two-component model for interpretation of the FF i…