Characteristics of different ionospheric layers

Characteristics of different ionospheric layers

The ionosphere is divided meteorologically into different regions or layers and each layer exhibit different characteristics.

The layers of the ionosphere are:

  • D-Layer
  • E-Layer
  • Es-Layer
  • F1-Layer
  • F2-Layer
Ionospheric Layers
Ionospheric Layers

1. Characteristics of D-Layer:

  • It is the lowest layer of the ionosphere.
  • It exists at an average height of 70 km.
  • Its thickness is 10 km.
  • It exists only in day-time.
  • Its ionization properties depend on the altitude of the sun above the horizon.
  • It is not a useful layer for HF communication.
  • It reflects some VLF and LF waves.
  • It absorbs MF and HF waves to some extent.
  • Its electron density, N = 400 electrons/cm3.
  • Its virtual height is 60 to 80 km.
  • Critical frequency of the layer, fc = 180 kHz.

2. Characteristics of E-Layer:

  • It exists next to D-Layer.
  • It exists at an average height of 100 km.
  • Its thickness is about 25 km.
  • It exists only in day-time.
  • The ions are recombined into molecules due to the absence of sun at night.
  • It reflects some HF waves in day-time.
  • It disappears at nights.
  • Its electron density, N = 2 × 105 electrons/cm3.
  • Its virtual height = 110 km.
  • Its critical frequency, fc ≈ 4 MHz.
  • Maximum single-hop range ≈ 2350 Km.

3. Characteristics of Es-Layer:

  • It is a sporadic E-Layer.
  • Its appearance is sporadic in nature.
  • If at all it appears, it exists in both day and night.
  • It is a thin layer.
  • Its ionization density is high.
  • It appears close to E-Layer.
  • If it appears, it provides good reception.
  • It is not a dependable layer for communication.

4. Characteristics of F1-Layer:

  • It exists at a height of about 180 km in day-time.
  • Its thickness is about 20 km.
  • It combines with F2-Layer during nights.
  • HF waves are reflected to some extent.
  • It absorbs HF to a considerable extent.
  • It passes on some HF waves towards F2-layer.
  • It’s virtual height ≈ 180 km.
  • Its critical frequency, fc ≈ 5 MHz.
  • Maximum single-hop range ≈ 3,000 km.

5. Characteristics of F2-Layer:

  • It is the most import layer for HF communication.
  • Its average height is about 325 km in day-time.
  • Its thickness is about 200 km.
  • It falls to a height of 300 km at nights as it combines with the F1-Layer.
  • The height of F2-Layer varies drastically with the time of the day, the average ambient temperature and sunspot cycle.
  • It exists at nights also.
  • It is the topmost layer of the ionosphere.
  • It is highly ionized.
  • It offers better HF reflection and hence reception.
  • Electron density of F-Layer, N = 2 × 106 electrons/cm3.
  • Its virtual height = 300 km in day-time and 350 km in the night.
  • Its critical frequency, fc ≈ 8 MHz in day-time and fc ≈ 6 MHz at nights.
  • Maximum single-hop range ≈ 3,800 km during day-time and 4,100 km at night.

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