Motions of H?-spicules along the solar limb

Abstract

A series of Ha-spectrograms obtained with the 21 in. Lyot coronagraph has been examined. Measurements of relative distances between spicules (nearly 50 features) embrace the time interval of about 21 min (38 pictures). It is found out that spicules oscillate along the limb with a characteristic time interval (period) about 1 min, characteristic amplitude of 1 arc sec and velocities about 10-15 km/s. The oscillations show no correlation for distant spicules.As was established by numerous observators, Doppler velocities of many features change as a function of time (Mouradian, 1965, Pasachoff et al., 1968, Nikolsky and Sazanov, 1966. The latter two papers state that all spicules, or at least some part of them, reverse the sign of line-of-sight velocities during their life-time, the latter usually being several times longer than the characteristic time of the line-of-sight velocity evolution (see also Beckers, 1968).The reasons for quasiperiodic oscillations of line-of-sight velocities are not clear. As was noted before by Nikolsky (1970) either (a) backward-translational mass movement along the spicule axis or (b) oscillations in the tangential direction (along the solar limb) are possible. The latter point of view seems more acceptable.The first mention of observations of spicule motions along the limb was made by Pasachoffet al. (1968). ObservationsThe observations discussed below were carried out on April 3, 1969 with the 53 cm Lyot coronograph mounted at the High Altitude Astronomical Station near Kislovodsk. 38 He spectrograms of the chromosphere were obtained during about 21 min. The observations were made by one of the authors assisted by Y. V. Platov and A. A. Sazanov. The curved slit of the spectrograph was adjusted concentric to the limb of the Sun at a height of 4200 km. Height and concentricity were controlled to within 0.5 arc sec using a method proposed by Nikolsky (1970). The dispersion is 0.96 A/mm, the scale is 16 arc sec per mm. The time interval between successive frames varied from 14 to 100 s, being on the average 30 s. The exposure time was 0.3 s. 35 mm isopanchromatic film Type-17 was developed with Kodak D-19 for 6 min at a temperature of 20 ~ The quality of the photographs is good and the resolution on each of them is not worse than 1 arc sec. Measurements of SpectrogramsWe used a one-coordinate measuring microscope with a scale division of 1 #. Readings were taken in the direction perpendicular to the dispersion and coinciding with a Solar Physics 18 (1971) 403-409. All Rights Reserved Copyright 9

Observation of kink waves in solar spicules

“…Oscillations in spicules with ∼5 min period have been detected by ground based (Kulidzanishvili & Zhugzhda 1983) and recently by space observations (De Pontieu et al 2003;Xia et al 2005). On theother-hand, oscillations in spicules with shorter period have been reported more than 30 years ago by Nikolsky & Platova (1971). They found that spicules oscillate along the limb with a characteristic period of about 1 min.…”

“…If spicules are formed in thin magnetic flux tubes, then the periodic transverse displacement of the axis observed by Nikolsky & Platova (1971) probably was due to the propagation of kink waves. It is well known that transverse kink waves can be generated in photospheric magnetic tubes by buffeting of granular motions (Roberts 1979;Hollweg 1981;Spruit 1981;Hasan & Kalkofen 1999).…”

High-cadence observations of spicular-type events on the Sun

“…Furthermore, they noted a period of oscillation between 1 to 4 min, an amplitude of about 1 and a maximum lateral velocity of ∼15-25 km s −1 , very similar to the values derived in this work. Nikolsky & Platova (1971) showed that some spicules change their position along the slit, thereby showing a real horizontal component of velocity. Furthermore, they concluded that spicules can execute quasi-periodic oscillations parallel to the limb with a period of ∼1 min, an amplitude of 1 and velocities around 10-15 km s −1 , similar to the more recent work cited above.…”

Withdrawn Article

“…The transverse displacement in spicules was initially noted by Nikolsky & Platova (1971) within solar limb observations. The authors showed that some spicules change their position along the slit, thereby showing a horizontal component of velocity.…”