On Differentiating Multiple Types of ULF Magnetospheric Waves in Response to Solar Wind Periodic Density Structures.

Identifying the nature and source of ultra-low frequencies (ULF) waves (f ⪅ 4 mHz) at discrete frequencies in the Earth's magnetosphere is a complex task. The challenge comes from the simultaneous occurrence of externally and internally generated waves, and the ability to robustly identify such perturbations. Using a recently developed robust spectral analysis procedure, we study an interval that exhibited in magnetic field measurements at geosynchronous orbit and in-ground magnetic observatories both internally supported and externally generated ULF waves. The event occurred on 9 November 2002 during the interaction of the magnetosphere with two interplanetary shocks that were followed by a train of 90 min solar wind periodic density structures. Using the Wang-Sheeley-Arge model, we mapped the source of this solar wind stream to an active region and a mid-latitude coronal hole just prior to crossing the Heliospheric current sheet. In both the solar wind density and magnetospheric field fluctuations, we separated broad power increases from enhancements at specific frequencies. For the waves at discrete frequencies, we used the combination of satellite and ground magnetometer observations to identify differences in frequency, polarization, and observed magnetospheric locations. The magnetospheric response was characterized by: (a) forced breathing by periodic solar wind dynamic pressure variations below ≈1 mHz, (b) a combination of directly driven oscillations and wave modes triggered by additional mechanisms (e.g., shock and interplanetary magnetic field discontinuity impact, and substorm activity) between ≈1 and 4 mHz, and (c) largely triggered modes above ≈4 mHz.

Geomagnetic activity, humidity, temperature and headache: is there any correlation?

Meterological factors influence several biological functions. Geomagnetic activity (GMA) can be considered a trigger factor of migraine attacks. We studied the possible relationship between 40 migraine patients and some meteorological factors: humidity, temperature and geomagnetic activity in particular. All frequency changes of geomagnetic activity, temperature and humidity values are recorded daily. The study was performed from March to June 1988 over a geographically small area in order to avoid climatic and environmental influences. Our results indicate a significant correlation between geomagnetic activity and migraine attack frequency. Controversial opinions concerning the modalities of data collection and the possible relationships between environment and headache raise the need of further studies.