Anti-sidereal time
Encyclopedia
Anti-sidereal time and extended-sidereal time are artificial time scale
s used to analyze the daily variation in the number of cosmic ray
s received on Earth
. Anti-sidereal time has about 364.25 days per year, one day less than the number of days in a year of solar time
, 365.25. Thus each anti-sidereal day is longer than a solar day (24) by about four minutes or 244. Extended-sidereal time has about 367.25 days per year, one day more than the number of days in a year of sidereal time
, 366.25. Thus each extended-sidereal day is shorter than a sidereal day (2356) by about four minutes or 2352. All years mentioned have the same length.
al velocity around the Sun. Other daily variations in amplitude in sidereal time are caused by the anisotropy
in the direction from which cosmic rays are received relative to the plane of our Milky Way
galaxy
. Both are contaminated by an annual seasonal variation. The daily solar variation is amplitude modulated
by the seasonal variation of , producing sideband
s on either side of the solar frequency, about , of and . Similarly, an annual amplitude modulation of of the sidereal frequency, about , produces sidebands of and . The upper sideband of the solar frequency contaminates the amplitude of the sidereal frequency, while the lower sideband of the sidereal frequency contaminates the amplitude of the solar frequency. Because the magnitudes of the two sidebands produced by amplitude modulation of the solar frequency are the same and no known natural phenomenon recurs at , the spurious amplitude at the sidereal frequency can be corrected by subtracting any signal present at the anti-sidereal frequency. Similarly, the spurious amplitude in the solar frequency of per year can be corrected by subtracting any signal present at the extended-sidereal frequency of per year.
Time scale
A time scale specifies divisions of time.*Time standard, a specification of either the rate at which time passes, or points in time, or both*Duration , a quantity of time...
s used to analyze the daily variation in the number of cosmic ray
Cosmic ray
Cosmic rays are energetic charged subatomic particles, originating from outer space. They may produce secondary particles that penetrate the Earth's atmosphere and surface. The term ray is historical as cosmic rays were thought to be electromagnetic radiation...
s received on Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
. Anti-sidereal time has about 364.25 days per year, one day less than the number of days in a year of solar time
Solar time
Solar time is a reckoning of the passage of time based on the Sun's position in the sky. The fundamental unit of solar time is the day. Two types of solar time are apparent solar time and mean solar time .-Introduction:...
, 365.25. Thus each anti-sidereal day is longer than a solar day (24) by about four minutes or 244. Extended-sidereal time has about 367.25 days per year, one day more than the number of days in a year of sidereal time
Sidereal time
Sidereal time is a time-keeping system astronomers use to keep track of the direction to point their telescopes to view a given star in the night sky...
, 366.25. Thus each extended-sidereal day is shorter than a sidereal day (2356) by about four minutes or 2352. All years mentioned have the same length.
Amplitude modulation sidebands
Cosmic rays received on Earth exhibit daily variations in amplitude in solar time due to the distribution of cosmic rays in the inner heliosphere and to the Compton-Getting effect caused by Earth's orbitOrbit
In physics, an orbit is the gravitationally curved path of an object around a point in space, for example the orbit of a planet around the center of a star system, such as the Solar System...
al velocity around the Sun. Other daily variations in amplitude in sidereal time are caused by the anisotropy
Anisotropy
Anisotropy is the property of being directionally dependent, as opposed to isotropy, which implies identical properties in all directions. It can be defined as a difference, when measured along different axes, in a material's physical or mechanical properties An example of anisotropy is the light...
in the direction from which cosmic rays are received relative to the plane of our Milky Way
Milky Way
The Milky Way is the galaxy that contains the Solar System. This name derives from its appearance as a dim un-resolved "milky" glowing band arching across the night sky...
galaxy
Galaxy
A galaxy is a massive, gravitationally bound system that consists of stars and stellar remnants, an interstellar medium of gas and dust, and an important but poorly understood component tentatively dubbed dark matter. The word galaxy is derived from the Greek galaxias , literally "milky", a...
. Both are contaminated by an annual seasonal variation. The daily solar variation is amplitude modulated
Amplitude modulation
Amplitude modulation is a technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. AM works by varying the strength of the transmitted signal in relation to the information being sent...
by the seasonal variation of , producing sideband
Sideband
In radio communications, a sideband is a band of frequencies higher than or lower than the carrier frequency, containing power as a result of the modulation process. The sidebands consist of all the Fourier components of the modulated signal except the carrier...
s on either side of the solar frequency, about , of and . Similarly, an annual amplitude modulation of of the sidereal frequency, about , produces sidebands of and . The upper sideband of the solar frequency contaminates the amplitude of the sidereal frequency, while the lower sideband of the sidereal frequency contaminates the amplitude of the solar frequency. Because the magnitudes of the two sidebands produced by amplitude modulation of the solar frequency are the same and no known natural phenomenon recurs at , the spurious amplitude at the sidereal frequency can be corrected by subtracting any signal present at the anti-sidereal frequency. Similarly, the spurious amplitude in the solar frequency of per year can be corrected by subtracting any signal present at the extended-sidereal frequency of per year.