Magnetic Signatures of low- to mid-Latitude Ionospheric Irregularities as Oobserved by CHAMP from 2000 to 2008

Details Magnetic Signatures of low- to mid-Latitude Ionospheric Irregularities as Oobserved by CHAMP from 2000 to 2008 Magnetic Signatures of low- to mid-Latitude Ionospheric Irregularities as Oobserved by CHAMP from 2000 to 2008

May 2009

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009agusmsa23a..01p&link_type=abstract

American Geophysical Union, Spring Meeting 2009, abstract #SA23A-01

Other

2400 Ionosphere (6929), 2415 Equatorial Ionosphere, 2439 Ionospheric Irregularities, 2443 Midlatitude Ionosphere, 2481 Topside Ionosphere

Scientific paper

We investigate the magnetic signatures of low- to mid-latitude ionospheric irregularities as observed by the CHAMP satellite. Equatorial plasma bubbles (EPBs) and low-latitude plasma blobs are accompanied by variations of magnetic field strength (magnetic pressure), which balances the change in plasma pressure. These features also show magnetic fluctuations perpendicular to the mean field, implying that field-aligned currents (FACs) are flowing around the irregularities. EPB Poynting flux in events occurring before 21LT, when they evolve actively, is directed downward along the magnetic field lines. This implies that FACs are driven by a high-altitude equatorial source. Perpendicular magnetic deflections of EPBs are tilted westward from the magnetic meridional direction, implying that the depleted volume of EPBs and the FAC structures are tilted westward above the magnetic equator. The peak-to-peak amplitude of the FAC density is found to range between 0.1-0.5 μA/m2. Blobs have a field-aligned structure spanning several hundred kilometers. And their magnetic properties corroborate the close relationship between EPBs and blobs. Medium-scale traveling ionospheric disturbances (MSTIDs) also have clear magnetic signatures perpendicular to the mean field with a good linear polarization. However, they are generally not accompanied by variations of the magnetic field strength at CHAMP altitudes (~400 km). MSTID magnetic signatures are practically absent above the southern Atlantic ocean and weak during the solar minimum. It means that other factors than MSTIDs, e.g. ionospheric conductivity, sporadic E-layer or plasma instabilities may play a non-negligible role in generating the FACs. The peak-to-peak amplitude of the FAC density also ranges between 0.1-0.5 μA/m2.

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