A brief review of “solar flare effects” on the ionosphere

Abstract

[1] The study of solar flare effects (SFEs) on the ionosphere is having a renaissance. The development of GPS ground and satellite data for scientific use has opened up new means for high time resolution research on SFEs. At present, without continuous flare photon spectra (X rays, EUV, UV, and visible) monitoring instrumentation, the best way to model flare spectral changes within a flare is through ionospheric GPS studies. Flare EUV photons can increase the total electron content of the subsolar ionosphere by up to 30% in $5 min. Energetic particles (ions) of 10 keV to GeV energies are accelerated at the flare site. Electrons with energies up to several MeV are also created. A coronal mass ejection (CME) is launched from the Sun at the time of the flare. Fast interplanetary CMEs (ICMEs) have upstream shocks which accelerate ions to $10 keV to $10 MeV. Both sources of particles, when magnetically connected to the Earth's magnetosphere, enter the magnetosphere and the high-latitude and midlatitude ionosphere. Those particles that precipitate into the ionosphere cause rapid increases in the polar atmospheric ionization, disruption of transpolar communication, and cause ozone destruction. Complicating the picture, when the ICME reaches the magnetosphere $1 to 4 days later, shock compression of the magnetosphere energizes preexisting 10-100 keV magnetospheric electrons and ions, causing precipitation into the dayside auroral zone ($60°-65°MLAT) ionospheres. Shock compression can also trigger supersubstorms in the magnetotail with concomitant energetic particle precipitation into the nightside auroral zones. If the interplanetary sheath or ICME magnetic fields are southwardly directed and last for several hours, a geomagnetic storm will result. A magnetic storm is characterized by the formation of an unstable ring current with energetic particles in the range $10 keV to $500 keV. The ring current decays away by precipitation into the middle latitude ionosphere over timescales of $10 h. A schematic of a time line for the above SFE ionospheric effects is provided. Descriptions of where in the ionosphere and in what time sequence is provided in the body of the text. Much of the terminology presently in use describing solar, interplanetary, magnetospheric, and ionospheric SFE-related phenomena are dated. We suggest physics-based terms be used in the future.

Geomagnetic storms: historical perspective to modern view

“…The particles with sufficient intensities can cause satellite damage and radiation hazards for man in space as well (National Research Council report 2008; Royal Academy of Engineering report 2013). A much greater delayed effect is the ICME which can take a fraction of a day (Vaisberg and Zastenker 1976;Tsurutani et al 2009) to days (Gonzalez and Tsurutani 1987;Gonzalez et al 1989;Feynman and Gabriel 2000;Mannucci et al 2005) to reach the Earth. With conditions of southwardly directed IMFs, the ICME and its sheath can cause geomagnetic storms and substorms (Rostoker and Falthammar 1967;Tsurutani and Meng 1972;Gonzalez et al 1989;Echer and Gonzalez 2008a;Echer et al 2008b).…”

“…The most energetic particles arrive in 10 s of min, but the greatest fluxes arrive in ~h. These energetic particles have access to the Earth's polar regions, causing ionization in those regions and worldwide radio blackouts (Tsurutani et al 2009). The particles with sufficient intensities can cause satellite damage and radiation hazards for man in space as well (National Research Council report 2008; Royal Academy of Engineering report 2013).…”

Short-term variability of the Sun-Earth system: an overview of progress made during the CAWSES-II period

“…In addition, if the shock remained strong, it would produce an extreme impulse on the magnetosphere that can expose geosynchronous orbit to the solar wind (Tsurutani and Lakhina 2014) and a sudden (positive) impulse (SI + ) on the ground ). An intense shock would also produce an extreme energetic storm particle (ESP) event at Earth (Tsurutani et al 2009b). Thus for solar terrestrial relationships, an extreme event in its origin will also have extreme consequences at Earth and nearEarth space environment.…”

Automatic detection of Sfe: a proposal

“…They also have different relaxation times (Richmond and Venkateswaran, 1971). Thus, to achieve a certain degree of certainty in the Service of Rapid Magnetic Variations (Curto et al, 2007), other contemporary ionospheric effects are usually sought out (Tsurutani et al, 2009). …”