Function Of Geomagnetic Activity Research Articles

Ultraviolet nightglow production near the magnetic equator by neutral particle precipitation

The near‐midnight latitudinal (±45) distribution of the O I 911‐Å, 1304‐Å, and 1356‐Å emissions, observed by the extreme ultraviolet (EUV) spectrometer on the STP 78‐1 satellite, have been analyzed and compared as a function of geomagnetic activity. The dominant source of these emissions is radiative recombination of atomic oxygen ions; however, for geomagnetically disturbed periods, excess O I 1304‐Å and 1356‐Å emission is observed within ±5° of the dip equator. Neutral particle precipitation from the ring current is discussed as a possible source of the excess O I 1304‐Å and 1356‐Å emission.

The Position and shape of the neutral sheet at 30-REdistance

An examination of Explorer 34 encounters with the neutral sheet reveals a much broader arching of the neutral sheet at 30 RE than closer to the earth at 20 RE. Further, the location of the neutral sheet hinging point in the geomagnetic equatorial plane is found to be a strong function of geomagnetic activity. For Kp less than 2 the apparent hinging distance is close to 11 RE. For Kp greater than 4 the apparent hinging distance is close to zero. This dependency reflects a negligible return of the neutral sheet to the solar magnetospheric equatorial plane with distance behind the earth at quiet times but reflects a rapid return at disturbed times, in addition to possible variations in the location of the hinging point in the geomagnetic equatorial plane.

Morphology of auroral electron energetic and angular distributions according to ‘Cosmos 261’ measurements

For tangential passes of northern and southern auroral zones average characteristics of electron precipitations diffuse background for energy range 1–150 keV and more were obtained. Pitch-angle distribution and spectral characteristics of this background remained constant for the satellite trajectories up to 5000–6000 km. This fact allows to obtain the pitch-angle electron distributions for eight energy intervals, spectral characteristics over auroral zones and in polar caps, diurnal variations of auroral electron distribution intensity, as a function of geomagnetic activity.

Experimental Evidence of the Directional Components of Cosmic Rays

It is possible to resolve the diurnal variation into two components. The first of these has its maximum at 18 h and corresponds to the particle wind predicted in the theory by Alfven (1954). The amplitude ought to be constant both as a function of geomagnetic activity and as a function of time. The second component has its maximum at 12 h . It represents the sum of the various kinds of radial particle flow, and it ought to display variations indirectly related to geomagnetic activity. A search for experimental evidence of these components is made possible through the determination of the incidental directions of the primary particles by Brunberg (1953) and Brunberg and Dattner (1953). An analysis of C.R. measurements from Stockholm, Nagoya, and Huancayo seems to confirm the two components and their expected properties. A very doubtful amplitude change of the 18 h -component during major magnetic storms is not at variance with theory. The Stockholm measurements were treated by Sandstrom (1955) as to geomagnetic effects, those from Nagoya and Huancayo by Sekido and Kodama (1952). A seasonal phase shift reported by the latter for geomagnetically quiet days is compared to measurements in Stockholm. If it exists at all the reported phase shift is evidently due to local effects. Other secular or seasonal phase shifts (Elliot and Thambyaphillai 1953) have not been treated in the present study, as the data did not provide any example of these effects. Several points are open to discussion because of the data's being collected with instruments of widely different properties. Directional counter telescopes offer the most valuable results, if they are designed for a comparatively small aperture and measure in at least two directions. DOI: 10.1111/j.2153-3490.1956.tb01193.x

Experimental Evidence of the Directional Components of Cosmic Rays

It is possible to resolve the diurnal variation into two components. The first of these has its maximum at 18h and corresponds to the particle wind predicted in the theory by ALFVÉN (1954). The amplitude ought to be constant both as a function of geomagnetic activity and as a function of time. The second component has its maximum at 12h. It represents the sum of the various kinds of radial particle flow, and it ought to display variations indirectly related to geomagnetic activity. A search for experimental evidence of these components is made possible through the determination of the incidental directions of the primary particles by BRUNBERG (1953) and BRUNBERG and DATTNER (1953). An analysis of C.R. measurements from Stockholm, Nagoya, and Huancayo seems to confirm the two components and their expected properties. A very doubtful amplitude change of the 18h-component during major magnetic storms is not at variance with theory. The Stockholm measurements were treated by SANDSTRÖM (1955) as to geomagnetic effects, those from Nagoya and Huancayo by SEKIDO and KODAMA (1952). A seasonal phase shift reported by the latter for geomagnetically quiet days is compared to measurements in Stockholm. If it exists at all the reported phase shift is evidently due to local effects. Other secular or seasonal phase shifts (ELLIOT and THAMBYAPHILLAI 1953) have not been treated in the present study, as the data did not provide any example of these effects. Several points are open to discussion because of the data’s being collected with instruments of widely different properties. Directional counter telescopes offer the most valuable results, if they are designed for a comparatively small aperture and measure in at least two directions.