Regular oscillations near 1 c/s observed at middle and low latitudes

Abstract

A review is presented of so me of th e more important prope rti es of Pc 1(0.2-5 cIs) e missions observed at middle and low lati tud es . Special attention is give n to fin e s tru c ture d regular osci ll ati ons referred to b y various workers as pearls, tYIJe A osc ill a tio ns, and h ydromagne ti c (hm) e mi ss ions. Th e fo ll ow· in g aspects of th ese oscillations are d isc ussed.(a) Signal appearance. Th e e mi ss ions are co nsid ere d fro m both th e ir a mplitud e· time (wave· fo rm) appearance observ ed o n c ha rt reco rd s a nd th e ir freq ue ncy-tim e ({t) c ha rac te ri s ti cs observed on so nagra ms. The various t ypes of {t fin e s tru c ture are discussed (ri sing a nd fa lling freq uency e le· me nt s, fan s ha ped e le me nts, e tc.).(b) SimuLtaniet y of ocwrrence at widely separated locations. A hi g h degree of similarity is often found in th e ap peara nce of {t s tru ctura l e leme nt s of hm e mi ss ions reco rd ed simult a neo usly a t wide ly se parate d s tati ons. Attention is give n to the time-s hifts be twee n th ese e le me nts at st ati ons in th e sa me he mi sp he re a nd in oppos it e he mi s phe res.(c) Time of occurrence. Co rre lati ons are co nsid e red be twee n tim es of occurrence of hm e mi ssio ns a nd other geop hys ica l effects s uc h as c ha rged parti c le even ts, magneti c s torm s, a nd variations of the io nos ph eric para me te r F oF2.(d) Latitude effects. Various latitude dependent e mi ss ion c hara c te ri s ti cs a re di sc ussed. These include latitude variations of e mi ss ion fre qu e ncy, fin e s tru c ture repetiti on pe ri od , a nd signa l a mplitude.In addition to th e aspects of th e Pc 1 emission s outlined above, properties of two oth er typ es of e mi ss ions are brie fl y discussed. One of these signals, referred to he re as a "continu ous e miss ion" also lies in th e Pc 1 category. It is often obsuved co ntinuous ly throu g hout th e ni ght and is c haracterized by a slow variation of J.t c haracte ri s ti cs. Th e other signal, whi c h might be pl aced in a P c 1-Pi 1 tran siti on ca tego ry, is observed durin g magneti ca ll y di sturbe d periods. On so nagram s it is c haracte rize d by an irregularly spaced ri sin g freq ue ncy fin e-s tru c ture. When monitore d aurally on ti me· co mpressed magnet ic tap e (speed-up fa cto r of 1000 to 2000), it is c hara cterized by a so und simil ar to bubbles blown unde r wate r.

Geomagnetic pulsations

“…Figure 3 summarizes the diurnal patterns reported by Benioff (1960), Schlich (1963), Saito (1964b), Fraser (1965), Heacock and Hessler (1965), Campbell and Stiltner (1965) and Troitskaya (1967). This fact leads to an obscure relation between the PP occurrence and Kp-index (Wentworth, 1964;Campbell and Stiltner, 1965;Matveyeva and Troitskaya, 1965;Tepley, 1965). The maximum time seems to shift gradually from the day-hours to the night-hours at about 60 ~ of geomagnetic latitude.…”

“…Researches on PP have rapidly increased since 1960 and about one third of the Amplitudes of PP often reach hundreds of milligammas at high latitudes, tens of milligammas at middle and low latitudes and up to ten milligammas in the equatorial regions (Tepley, 1965;Troitskaya, 1967;Heacock, 1968). Maximum amplitudes seem to be observed in sub-auroral to auroral zones (Troitskaya, 1967;Kenney and Knaflich, 1967).…”

Substorm aspects of magnetic pulsations

“…Another valuable result of this theory is the interpretation of the experimental T, t plots. When one plots for the different events observed in different places the repetition period T vs. the period of oscillation, t, one obtains points in a limited area of the T, t plane (Gendrin, 1963 ;Tepley, 1965). Figure 24 shows that this limited area is approximately the area for which the total amplification factor along the magnetic field line is greater than 5. .…”

Rapid Geomagnetic Field Variations Observed at Conjugate Locations

“…Schlicht (1963) reported some similarities in the records taken at Chambon-la-Foret and Garchy, France, and at Hermanus, South Mrica. The pc I at the near conjugate locations of Kauai and Tongatapu has been presented by Tepley (1964Tepley ( , 1965Tepley ( , 1966.…”