Statistical Study of the Effect of Different Solar Wind Types on Magnetic Storm Generation During 1995–2016

Abstract. The depression of the horizontal magnetic field at Earth's equator for the largest imaginable magnetic storm has been estimated (Vasyliūnas, 2011a) as −Dst ~ 2500 nT, from the assumption that the total pressure in the magnetosphere (plasma plus magnetic field perturbation) is limited, in order of magnitude, by the minimum pressure of Earth's dipole field at the location of each flux tube. The obvious related question is how long it would take the solar wind to supply the energy content of this largest storm. The maximum rate of energy input from the solar wind to the magnetosphere can be evaluated on the basis either of magnetotail stress balance or of polar cap potential saturation, giving an estimate of the time required to build up the largest storm, which (for solar-wind and magnetospheric parameter values typical of observed superstorms) is roughly between ~2 and ~6 h.

Download Full-text

Response of the inner and outer magnetosphere to solar wind density fluctuations during the recovery phase of a moderate magnetic storm

Journal of Atmospheric and Solar-Terrestrial Physics ◽

10.1016/j.jastp.2007.02.011 ◽

2007 ◽

Vol 69 (14) ◽

pp. 1707-1722 ◽

Cited By ~ 8

Author(s):

N. Zolotukhina ◽

V. Pilipenko ◽

M.J. Engebretson ◽

A.S. Rodger

Keyword(s):

Solar Wind ◽

Magnetic Storm ◽

Recovery Phase ◽

Density Fluctuations ◽

Solar Wind Density ◽

Outer Magnetosphere

Download Full-text

Extremely intense (SML ≤–2500 nT) substorms: isolated events that are externally triggered?

Annales Geophysicae ◽

10.5194/angeo-33-519-2015 ◽

2015 ◽

Vol 33 (5) ◽

pp. 519-524 ◽

Cited By ~ 30

Author(s):

B. T. Tsurutani ◽

R. Hajra ◽

E. Echer ◽

J. W. Gjerloev

Keyword(s):

Solar Wind ◽

Magnetic Fields ◽

Magnetic Storm ◽

Solar Wind Plasma ◽

Magnetic Storms ◽

Input Energy ◽

Stored Energy ◽

Ionospheric Currents ◽

Interplanetary Magnetic Fields ◽

Very High

Abstract. We examine particularly intense substorms (SML &leq;–2500 nT), hereafter called "supersubstorms" or SSS events, to identify their nature and their magnetic storm dependences. It is found that these intense substorms are typically isolated events and are only loosely related to magnetic storms. SSS events can occur during super (Dst &leq;–250 nT) and intense (−100 nT &geq; Dst >–250) magnetic storms. SSS events can also occur during nonstorm (Dst &geq;–50 nT) intervals. SSSs are important because the strongest ionospheric currents will flow during these events, potentially causing power outages on Earth. Several SSS examples are shown. SSS events appear to be externally triggered by small regions of very high density (~30 to 50 cm−3) solar wind plasma parcels (PPs) impinging upon the magnetosphere. Precursor southward interplanetary magnetic fields are detected prior to the PPs hitting the magnetosphere. Our hypothesis is that these southward fields input energy into the magnetosphere/magnetotail and the PPs trigger the release of the stored energy.

Download Full-text

Foreshock cavitons and spontaneous hot flow anomalies: A statistical study with a global hybrid-Vlasov simulation

10.5194/angeo-2020-87 ◽

2021 ◽

Author(s):

Vertti Tarvus ◽

Lucile Turc ◽

Markus Battarbee ◽

Jonas Suni ◽

Xóchitl Blanco-Cano ◽

...

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Rest Frame ◽

Statistical Study ◽

Plasma Temperature ◽

Propagation Speed ◽

Bow Shock ◽

Ulf Waves ◽

Subsequent Formation ◽

Comparable Amount

Abstract. The foreshock located upstream of Earth's bow shock hosts a wide variety of phenomena related to the reflection of solar wind particles from the bow shock and the subsequent formation of ultra-low frequency (ULF) waves. In this work, we investigate foreshock cavitons, which are transient structures resulting from the non-linear evolution of ULF waves, and spontaneous hot flow anomalies (SHFAs), which evolve from cavitons as they accumulate suprathermal ions while being carried to the bow shock by the solar wind. Using the global hybrid-Vlasov simulation model Vlasiator, we have conducted a statistical study in which we track the motion of individual cavitons and SHFAs in order to examine their properties and evolution. In our simulation run where the interplanetary magnetic field (IMF) is directed at a sunward-southward angle of 45 degrees, continuous formation of cavitons is found up to ~ 11 Earth radii (RE) from the bow shock (along the IMF direction), and caviton-to-SHFA evolution takes place within ~ 2 RE from the shock. A third of the cavitons in our run evolve into SHFAs, and we find a comparable amount of SHFAs forming independently near the bow shock. We compare the properties of cavitons and SHFAs to prior spacecraft observations and simulations, finding good agreement. We also investigate the variation of the properties as a function of position in the foreshock, showing that the transients close to the bow shock are associated with larger depletions in the plasma density and magnetic field magnitude, along with larger increases in the plasma temperature and the level of bulk flow deflection. Our measurements of the propagation velocities of cavitons and SHFAs agree with earlier studies, showing that the transients propagate sunward in the solar wind rest frame. We show that SHFAs have a greater solar wind rest frame propagation speed than cavitons, which is related to an increase in the magnetosonic speed near the bow shock.

Download Full-text

Foreshock cavitons and spontaneous hot flow anomalies: a statistical study with a global hybrid-Vlasov simulation

Annales Geophysicae ◽

10.5194/angeo-39-911-2021 ◽

2021 ◽

Vol 39 (5) ◽

pp. 911-928

Author(s):

Vertti Tarvus ◽

Lucile Turc ◽

Markus Battarbee ◽

Jonas Suni ◽

Xóchitl Blanco-Cano ◽

...

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Rest Frame ◽

Statistical Study ◽

Plasma Temperature ◽

Propagation Speed ◽

Bow Shock ◽

Ulf Waves ◽

Subsequent Formation ◽

Comparable Amount

Abstract. The foreshock located upstream of Earth's bow shock hosts a wide variety of phenomena related to the reflection of solar wind particles from the bow shock and the subsequent formation of ultra-low-frequency (ULF) waves. In this work, we investigate foreshock cavitons, which are transient structures resulting from the non-linear evolution of ULF waves, and spontaneous hot flow anomalies (SHFAs), which are thought to evolve from cavitons as they accumulate suprathermal ions while being carried to the bow shock by the solar wind. Using the global hybrid-Vlasov simulation model Vlasiator, we have conducted a statistical study in which we track the motion of individual cavitons and SHFAs in order to examine their properties and evolution. In our simulation run where the interplanetary magnetic field (IMF) is directed at a sunward–southward angle of 45∘, continuous formation of cavitons is found up to ∼11 Earth radii (RE) from the bow shock (along the IMF direction), and caviton-to-SHFA evolution takes place within ∼2 RE from the shock. A third of the cavitons in our run evolve into SHFAs, and we find a comparable amount of SHFAs forming independently near the bow shock. We compare the properties of cavitons and SHFAs to prior spacecraft observations and simulations, finding good agreement. We also investigate the variation of the properties as a function of position in the foreshock, showing that transients close to the bow shock are associated with larger depletions in the plasma density and magnetic field magnitude, along with larger increases in the plasma temperature and the level of bulk flow deflection. Our measurements of the propagation velocities of cavitons and SHFAs agree with earlier studies, showing that the transients propagate sunward in the solar wind rest frame. We show that SHFAs have a greater solar wind rest frame propagation speed than cavitons, which is related to an increase in the magnetosonic speed near the bow shock.

Download Full-text