Indian Scientists are tracking a very narrow band of intense electric current in the earth’s ionosphere called Equatorial ElectroJet to understand equatorial ionospheric processes important for GNSS-based navigation. Read here to learn more.
Scientists are tracking a very narrow band of intense electric current in the earth’s ionosphere called Equatorial ElectroJet through ground-based magnetometers in India’s southern tip.
They have developed an empirical model to understand the equatorial electrodynamical processes that can impact satellite orbital dynamics, Global Positioning Systems and other satellite communication links as well as electrical power grids.
Equatorial Electrojet (EEJ)
The Equatorial Electrojet (EEJ) is a narrow ribbon-like current that flows eastward along the Earth’s magnetic equator in the ionosphere (specifically, the E-region, approximately 90-130 km above the Earth’s surface).
This phenomenon is primarily driven by solar radiation and Earth’s magnetic field, producing unique electrical and magnetic conditions at equatorial latitudes.
The EEJ is particularly intense due to factors like geomagnetic field alignment, atmospheric conductivity, and the concentration of ionized particles near the magnetic equator.
Characteristics of the Equatorial Electrojet
- Location and Intensity: The EEJ is strongest within ±3° of the magnetic equator. It intensifies during the daytime due to increased ionization from solar radiation, which enhances conductivity. This current often weakens or even dissipates at night.
- Formation Mechanism:
- Solar heating causes temperature gradients in the ionosphere, leading to ionospheric winds and an eastward electric field. Near the magnetic equator, these electric fields interact with the geomagnetic field, resulting in a strong eastward current.
- This interaction creates a Hall effect, which intensifies the current flow in the E-region, forming the characteristic narrow, high-density current structure of the EEJ.
- Magnetic Effects: The EEJ induces magnetic variations detectable at ground level. Magnetometers placed at equatorial observatories often record these variations, providing essential data for studying ionospheric dynamics and geomagnetic field interactions.
Scientific Importance of the EEJ
- Space Weather and Navigation:
- The EEJ plays a role in understanding space weather impacts on communication and navigation systems. During geomagnetic storms, fluctuations in the EEJ affect ionospheric conditions, which in turn impact GPS accuracy and radio signal propagation.
- Electrodynamics Research:
- The EEJ offers insights into ionospheric electrodynamics and the behaviour of electric fields within Earth’s upper atmosphere. It serves as a natural laboratory for studying how solar activity influences Earth’s near-space environment.
- Global Electromagnetic Induction Studies:
- Changes in the EEJ influence Earth’s geomagnetic field and are studied to better understand the processes of global electromagnetic induction, including the way currents are induced within the Earth and its ionosphere.
Variability and Monitoring
The intensity of the EEJ fluctuates with the solar cycle, atmospheric conditions, and geomagnetic activity.
Researchers use ground-based magnetometers, satellites, and models to monitor and analyze EEJ behaviour.
Monitoring the EEJ can help in predicting space weather effects on technological systems, making it a critical area of study in geophysics and space science.
The model developed by Indian Scientists
Earth’s geomagnetic equator passes very close to the southern tip of India, where a unique and very strong current of the order of 100 kA known as Equatorial ElectroJet (EEJ), flows at around 105-110 km height in the upper atmosphere.
Due to this intense current jet, the geomagnetic field near the equator is uniquely enhanced by a few tens to a few hundreds of nanotesla (nT).
- Measuring this current intensity through the geomagnetic field enhancement provides an important understanding of the variation of the ionospheric electric field.
- Therefore, understanding and modelling of EEJ variations would have important applications in assessing the satellite orbital dynamics, Global Positioning Systems and other satellite communication links, electrical power grids, etc.
- Indian Institute of Geomagnetism (IIG) regularly measures this EEJ current using ground-based magnetometers located at an equatorial station Tirunelveli, very close to the southern tip of India.
Understanding the EEJ variations from long-term observations for more than two decades, scientists from IIG Navi Mumbai, an autonomous institute of the Department of Science and Technology, have developed an empirical model that can predict the EEJ current very accurately.
The research has been published in the journal Space Weather.
- This model, named “Indian Equatorial Electrojet (IEEJ) Model” is the first empirical model that can accurately predict the Equatorial Electrojet over the Indian sector and has been made publicly available.
- The model’s web interface facilitates the user to simulate the EEJ for any given date and solar activity conditions; and enables to obtain output in ASCII and/or PNG graphical formats.
- The model can be used to understand the unique equatorial ionospheric processes and can have applications in GNSS-based navigation/positioning, transmission lines, and the oil/gas industry that uses long-distance pipelines.
The model is available for the public at https://iigm.res.in/system/files/IEEJ_model.html
Magnetic Equator
The magnetic equator is an imaginary line encircling the Earth, positioned approximately halfway between the magnetic north and magnetic south poles, where the Earth’s magnetic field is horizontal to the surface.
It is different from the geographic equator, as it shifts slightly in response to changes in the Earth’s magnetic field.
Key Characteristics of the Magnetic Equator:
- Field Alignment: At the magnetic equator, the Earth’s magnetic field is aligned horizontally, meaning that the field lines run parallel to the surface. The magnetic inclination, or dip angle, is close to zero at this line, unlike at the poles where it is steep.
- Equatorial Electrojet: The magnetic equator is crucial in geomagnetism as it is associated with the equatorial electrojet, a narrow band of intense electric current that flows eastward in the ionosphere near the magnetic equator. This electrojet has a significant influence on magnetic variations observed near the equator, especially during solar events.
- Geographic Variations: Unlike the fixed geographic equator, the magnetic equator is not a straight line but rather an irregular path influenced by the distribution and changes in Earth’s magnetic field. It can shift due to geomagnetic secular variation, a phenomenon resulting from movements in the Earth’s core.
Importance of the Magnetic Equator:
- The magnetic equator is significant for navigation, ionospheric research, and satellite communications, as it affects the propagation of radio signals and impacts solar storm effects.
- The dynamics of the Earth’s magnetic field at the equator are also crucial in climate and environmental studies, particularly concerning how charged particles move in response to magnetic fields.
- By understanding the magnetic equator, scientists can better predict space weather effects and improve systems dependent on stable magnetic conditions, like GPS and satellite-based systems.
Magnetic equator vs Geographic equator
Geographic equator |
Magnetic equator |
The geographic equator is the imaginary line around the Earth that is equidistant from the North and South Poles, dividing the planet into the Northern and Southern Hemispheres. |
The magnetic equator, also known as the aclinic line, is an imaginary line around Earth where the magnetic field is horizontal, meaning there is no vertical component of the magnetic field. |
It is located at 0° latitude and is determined by Earth’s rotational axis. The geographic equator is fixed and aligns with the natural shape of the Earth, marking the point where the days and nights are roughly equal throughout the year. |
Unlike the geographic equator, the magnetic equator is not a fixed line and shifts due to changes in Earth’s magnetic field caused by factors such as the movement of molten iron in the Earth’s outer core. |
The geographic equator is primarily a reference line for geography, climate zones, and time zones. |
This line does not align with the geographic equator, as Earth’s magnetic poles are not precisely aligned with its geographic poles. |
Frequently Asked Questions (FAQs)
Q. Where is the magnetic equator in India?
Ans: It is located in Thumba, Thiruvananthapuram which is near the southern tip of mainland India, very close to Earth’s magnetic equator.
Q. What is the difference between geographic and magnetic equator?
Ans: The magnetic equator and the geographic equator are two distinct lines encircling Earth, differing in purpose, position, and the phenomena they represent.
- Position: While the geographic equator remains stable at 0° latitude, the magnetic equator varies and is typically located a few degrees north or south of the geographic equator.
- Movement: The magnetic equator shifts over time due to changes in Earth’s magnetic field, while the geographic equator remains constant.
- Purpose and Use: The magnetic equator is significant in geomagnetic studies and navigation as it influences compass readings and radio wave propagation. The geographic equator is primarily a reference line for geography, climate zones, and time zones.
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-Article by Swathi Satish
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