Interplanetary magnetic-sector structure

• Main Author: L. Svalgaard
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 1972
• Subjects: Christensen; Resolute Bay
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.380.4143; http://www.leif.org/research/JA077i022p04027.pdf

The influence of the direction of the interplanetary magnetic field on the geomagnetic field at high latitudes is used to study the long-term behavior of the sector structure during nearly four solar cycles. It is found that the rotation period of the sector structure varies from about 28.5 days in the beginning of a solgr cycle to 27.0 days in the end. Also it is shown that short-lived sectors rotate more slowly than long-lived ones. Geomagnetic effects related to the interplane- perturbation classfries the day as type A. An tary magnetic field. A relation between the observer using magnetograms from a southern polarity of the interplanetary magnetic field polar-cap station should adopt the definition and the type of diurnal variation of the geomag- that a positive Z perturbation is directed toward netic field inside the polar cap has been dis- the earth. In general, the regularity of the covered independently by Svalgaard [1968], magnetograms leaves little doubt about the type Mansurov [1969], and Mansurov and Man- of perturbation. With very few exceptions it is surova [1970] and noted by Iwasaki [1971]. possible to classify every day. Figure 2 shows The relationship has been confirmed by Friis- some sequences of Z records from Resolute Bay Christensen et al. [1971]. The most pronounced (84.3 ø invariant latitude). It is clearly seen effect, a broad perturbation of the geomagnetic that the same type persists through several days. field lasting for several hours, is found in the In some of the sequences a change of type is vertical component Z of the field on stations demonstrated. near the invariant poles. Figure i shows mag- This classification was actually developed benetograms from the near-conjugate stations Thule (86.8 ø invariant latitude) and Vostok- 61700-(--84.9 ø invariant latitude). To increase readability, all magnetograms in this paper have-61600been redrawn on the basis of hourly mean U values. When the earth lies in a polarity sector THULE of the interplanetary magnetic field away from the sun, ...