(Un)Explained EMIC Waves: Understanding Quiet Time EMIC Wave Drivers

Result code in IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F68378289%3A_____%2F25%3A00638391" target="_blank" >RIV/68378289:_____/25:00638391 - isvavai.cz</a>

Result on the web

<a href="https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2024JA033125" target="_blank" >https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2024JA033125</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1029/2024JA033125" target="_blank" >10.1029/2024JA033125</a>

Result language

angličtina

Original language name

(Un)Explained EMIC Waves: Understanding Quiet Time EMIC Wave Drivers

Original language description

Electromagnetic ion cyclotron (EMIC) waves are known to be generated through cyclotron resonance with the local ion particle population and grow when there is a large enough temperature anisotropy. In general, these temperature anisotropies necessary for wave growth are found to be associated with either solar wind pressure pulses or particle injections during geomagnetic storms or substorms. However, some EMIC events do not show any clear association with these known drivers and appear unexplained. In our analysis of high-amplitude (> 1 nT) non-storm time EMIC waves, we find that 24 out of the 223 (similar to 11%) EMIC events with peak amplitude greater than 1 nT were not found to be associated with any clear EMIC wave driver. This raises a compelling question: What magnetospheric or solar wind driver provides the free energy to grow these quiet-time EMIC waves? Here, we examine two EMIC events on 13 April 2017 and 13 February 2014, which were excited during extremely quiet solar wind and geomagnetic conditions. An in-depth analysis of field and particle measurements from multiple data sets, including ground and in situ data for these two events, indicates that extremely weak and otherwise insignificant pressure values and/or very weak substorm injections occurring multiple hours before the event play a significant role in quiet time wave generation. Plain Language Summary Electromagnetic cyclotron (EMIC) waves can be found in Earth's magnetosphere. Here, these waves can then impact the space environment by causing the loss of radiation belt electrons and ring current protons. The loss of energetic particles impacts the environment of satellites, as well as the dynamics in the middle atmosphere chemistry where these particles ultimately are lost. Understanding when these waves are occurring and, thus, when we expect to see these impacts is important. Typically, EMIC waves are associated with pressure pulses from the solar wind and/or geomagnetic storms or substorms. However, similar to 11% of high amplitude, non-storm time EMIC waves are not associated with these known drivers. Within this paper, we look closely at two quiet time events and provide new insight into what drives this portion of the waves.

Czech name

—

Czech description

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Type

J_imp - Article in a specialist periodical, which is included in the Web of Science database

CEP classification

—

OECD FORD branch

10305 - Fluids and plasma physics (including surface physics)

Project

—

Continuities

I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Publication year

2025

Confidentiality

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Name of the periodical

Journal of Geophysical Research-Space Physics

ISSN

2169-9380

e-ISSN

2169-9402

Volume of the periodical

130

Issue of the periodical within the volume

8

Country of publishing house

US - UNITED STATES

Number of pages

19

Pages from-to

e2024JA033125

UT code for WoS article

001549635300001

EID of the result in the Scopus database

2-s2.0-105012871064