Condegram spiral plot
Encyclopedia
The Condegram spiral plot is an illustrative device developed by Dr. Mark Conde, Associate Professor at the University of Alaska, Fairbanks
to display space weather
data. Space weather effects on Earth are ultimately driven by processes originating with the Sun
, many of which are communicated to Earth by the hot plasma
which streams out from the Sun, called the solar wind
. Solar wind properties such as velocity, density, temperature and magnetic field are dependent upon conditions in the solar atmosphere, and are related either directly or indirectly to space weather effects observed on Earth, such as the aurora
.
) near the solar equator (however this period varies with solar latitude). This solar rotation can modulate the solar wind as observed from Earth, by bringing active regions in the Sun’s atmosphere (particularly coronal
holes) into and out of alignment with Earth.
The condegram spiral plot exploits the close connection between solar wind properties, their effect on space weather, and their modulation by the solar rotation
period. A given solar wind parameter (for example velocity) is plotted against a time axis which wraps around a circle (the ordinate therefore points radially outward). The time axis is scaled such that a full revolution around the circle corresponds to 27 days, and the radial distance of the axis from the center of the circle is made to increase with azimuthal angle, allowing the time axis to continue wrapping around the circle in an outward-moving spiral.
The great utility of the plot format is that a line of fixed azimuth (i.e. along a radial line from the center of the circle) essentially tracks a fixed location on the ‘surface’ of the Sun. For example, coronal holes allow fast-moving plasma to escape from the photosphere, which can effect a local increase in the solar wind speed. The solar wind speed will then be modulated by the Sun’s rotation, and hence a condegram spiral plot of solar wind speed would show a recurrent period of elevated speed at a fixed azimuth on the circle. The condegram can then be used as a tool for predicting when space weather effects might be more likely to be observed on Earth, which can be useful to space physics researchers and amateur aurora watchers.
University of Alaska Fairbanks
The University of Alaska Fairbanks, located in Fairbanks, Alaska, USA, is the flagship campus of the University of Alaska System, and is abbreviated as Alaska or UAF....
to display space weather
Space weather
Space weather is the concept of changing environmental conditions in near-Earth space or thespace from the Sun's atmosphere to the Earth's atmosphere. It is distinct from the concept ofweather within the Earth's planetary atmosphere...
data. Space weather effects on Earth are ultimately driven by processes originating with the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
, many of which are communicated to Earth by the hot plasma
Plasma (physics)
In physics and chemistry, plasma is a state of matter similar to gas in which a certain portion of the particles are ionized. Heating a gas may ionize its molecules or atoms , thus turning it into a plasma, which contains charged particles: positive ions and negative electrons or ions...
which streams out from the Sun, called the solar wind
Solar wind
The solar wind is a stream of charged particles ejected from the upper atmosphere of the Sun. It mostly consists of electrons and protons with energies usually between 1.5 and 10 keV. The stream of particles varies in temperature and speed over time...
. Solar wind properties such as velocity, density, temperature and magnetic field are dependent upon conditions in the solar atmosphere, and are related either directly or indirectly to space weather effects observed on Earth, such as the aurora
Aurora (astronomy)
An aurora is a natural light display in the sky particularly in the high latitude regions, caused by the collision of energetic charged particles with atoms in the high altitude atmosphere...
.
Solar Wind Data
As viewed from Earth the rotation period of the Sun is approximately 27 days (see Carrington rotationCarrington rotation
The Carrington rotation of the Sun is a system for comparing locations on the Sun over a period of time, allowing the following of sunspot groups or reappearance of eruptions at a later time....
) near the solar equator (however this period varies with solar latitude). This solar rotation can modulate the solar wind as observed from Earth, by bringing active regions in the Sun’s atmosphere (particularly coronal
Coronal loop
Coronal loops form the basic structure of the lower corona and transition region of the Sun. These highly structured and elegant loops are a direct consequence of the twisted solar magnetic flux within the solar body. The population of coronal loops can be directly linked with the solar cycle; it...
holes) into and out of alignment with Earth.
The condegram spiral plot exploits the close connection between solar wind properties, their effect on space weather, and their modulation by the solar rotation
Solar rotation
Solar rotation is able to vary with latitude because the Sun is composed of a gaseous plasma. The rate of rotation is observed to be fastest at the equator , and to decrease as latitude increases...
period. A given solar wind parameter (for example velocity) is plotted against a time axis which wraps around a circle (the ordinate therefore points radially outward). The time axis is scaled such that a full revolution around the circle corresponds to 27 days, and the radial distance of the axis from the center of the circle is made to increase with azimuthal angle, allowing the time axis to continue wrapping around the circle in an outward-moving spiral.
The great utility of the plot format is that a line of fixed azimuth (i.e. along a radial line from the center of the circle) essentially tracks a fixed location on the ‘surface’ of the Sun. For example, coronal holes allow fast-moving plasma to escape from the photosphere, which can effect a local increase in the solar wind speed. The solar wind speed will then be modulated by the Sun’s rotation, and hence a condegram spiral plot of solar wind speed would show a recurrent period of elevated speed at a fixed azimuth on the circle. The condegram can then be used as a tool for predicting when space weather effects might be more likely to be observed on Earth, which can be useful to space physics researchers and amateur aurora watchers.
Other Parameter Data
In addition to solar wind parameters (velocity, density, magnetic field), other common condegram parameters include geomagnetic indices and solar spectral fluxes. The plot format has been used to display bulk velocity, density and temperature data from the PLAsma and SupraThermal Ion Composition (PLASTIC) instrument aboard the STEREO satellites using software called SPLAT (STEREO PLASTIC Analysis Tool).External links
- Mark Conde's website:http://fulcrum.gi.alaska.edu/condegrm/xray_cgm.png,
- STEREOSTEREOSTEREO is a solar observation mission. Two nearly identical spacecraft were launched into orbits that cause them to respectively pull farther ahead of and fall gradually behind the Earth...
Main Website:http://stereo.jhuapl.edu/, - PLASTIC website:http://fiji.sr.unh.edu/STEREO_A_proton_condegrams_static.html,
- Lynch Rocket Lab, Dartmouth: http://www.dartmouth.edu/~aurora/swspeed.html
