Longitude

About: Longitude is a research topic. Over the lifetime, 2260 publications have been published within this topic receiving 54988 citations. The topic is also known as: angle of longitude.

The Influence of Planets on the Formation of Sun-Spots

Abstract: This investigation deals with the correlation between the position of sun-spots at their first appearance and the heliocentric longitude of the principal planets. The available data reach back as far as 1874 inclusive, and are to be found in the publications of the Royal Observatory, Greenwich. If we neglect the angle between the sun’s equator and the ecliptic, and add the heliocentric longitude of the earth to the longitude of a spot referred to the central meridian, we obtain the heliocentric longitude of the sun-spot measured from the first point of Aries; deducting now the heliocentric longitude of a planet, we obtain the longitude of the spot referred to the central meridian as seen from the planet. Excluding spots near the eastern limb, many of which have been formed on the invisible hemisphere and are brought into view by the sun’s rotation, the first photograph on which a spot appears gives the position of its origin within about 13° of longitude, provided there are no gaps in the daily records. For the reason given, no account has been taken of any spot which is first seen within 30° longitude from the eastern limb. Measured on the projected disc, the excluded portion covers at the equator a width of 2 minutes of arc or about the eighth part of the solar radius. The total number of spots dealt with is 4271.

Longitudinal Variation of the Lunar Tide in the Equatorial Electrojet

Abstract: The atmospheric lunar tide is one known source of ionospheric variability. The subject received renewed attention as recent studies found a link between stratospheric sudden warmings and amplified lunar tidal perturbations in the equatorial ionosphere. There is increasing evidence from ground observations that the lunar tidal influence on the ionosphere depends on longitude. We use magnetic field measurements from the CHAMP satellite during July 2000–September 2010 and from the two Swarm satellites during November 2013–February 2017 to determine, for the first time, the complete seasonal-longitudinal climatology of the semidiurnal lunar tidal variation in the equatorial electrojet intensity. Significant longitudinal variability is found in the amplitude of the lunar tidal variation, while the longitudinal variability in the phase is small. The amplitude peaks in the Peruvian sector (∼285∘E) during the Northern-Hemisphere winter and equinoxes, and in the Brazilian sector (∼325∘E) during the Northern-Hemisphere summer. There are also local amplitude maxima at ∼55∘E and ∼120∘E. The longitudinal variation is partly due to the modulation of ionospheric conductivities by the inhomogeneous geomagnetic field. Another possible cause of the longitudinal variability is neutral wind forcing by nonmigrating lunar tides. A tidal spectrum analysis of the semidiurnal lunar tidal variation in the equatorial electrojet reveals the dominance of the westward-propagating mode with zonal wavenumber 2 (SW2), with secondary contributions by westward-propagating modes with zonal wavenumber 3 (SW3) and 4 (SW4). Eastward-propagating waves are largely absent from the tidal spectrum. Further study will be required for the relative importance of ionopsheric conductivities and nonmigrating lunar tides.