1. Electricity in the AtmosphereLightning is, of course, an
electrical disturbance, much of which can be explained by the basic
principles of atmospheric electricity. You know from Chapter 1 that ions
(charged particles) are most abundant high in the atmosphere (in the
ionosphere, from about 80 to 500 km, or 50 to 300 mi). The upper
atmosphere has a positive charge, just as we find near the positive pole
of a battery. In the same way that a battery stores energy, electrical
charges in the atmosphere represent stored energy and have the potential
to do work. For both batteries and the atmosphere, this electrical
potential is expressed by voltage, which is simply the energy per unit
charge. For example, if a battery is rated at 1.5 volts (V), it means
that 1.5 joules are available per coulomb of charge (1.5 J/C). A coulomb
(C) is equivalent to the charge carried by about 6 × 1019 electrons.
The higher the voltage, the greater the energy release for each coulomb
transferred.In the case of Earth, a huge voltage difference exists
between the surface and the ionosphere—about 400,000 volts! This voltage
gradient sets up what we call the fair-weather electric field. The
fair-weather field is always present, even in bad weather, so a better
name might be the mean electric field. The fair-weather field can be
thought of as the background situation on which extreme events such as
lightning are superimposed.Does electricity flow in response to the
voltage gradient of the fair-weather field? Yes, but because air is a
good insulator, the current is weak, about 2000 coulombs per second
(2000 Ampere) for the entire planet. In North America, individual houses
are typically wired for 200-Ampere service, so we see that the
atmospheric current is truly very small. Nevertheless, it does represent
a continuous leakage, whereby electrons are transferred from the
surface or, equivalently, positive charges are transferred from the
atmosphere. This implies that for the mean electric field to be
maintained, it must be continuously replenished. As a matter of fact,
lightning discharges in thunderstorms are thought to be the primary
recharge mechanism. In other words, cloud-to-ground lightning discharges
transfer electrons to the surface, maintaining the voltage difference
and the resulting electric field.In the lower atmosphere, the
fair-weather electric field gradient is on the order of 100 V per meter.
(Although this might sound impressive, remember that few ions are
present, so the total available energy is very low.) Of course, for
lightning to occur, the field strength must be greatly intensified above
the background value. How this happens can be only partly explained
today, nearly 250 years after Ben Franklin performed his famous kite
experiment.What is the fair-weather electric field? Get solution
2. Electricity in the AtmosphereLightning is, of course, an electrical disturbance, much of which can be explained by the basic principles of atmospheric electricity. You know from Chapter 1 that ions (charged particles) are most abundant high in the atmosphere (in the ionosphere, from about 80 to 500 km, or 50 to 300 mi). The upper atmosphere has a positive charge, just as we find near the positive pole of a battery. In the same way that a battery stores energy, electrical charges in the atmosphere represent stored energy and have the potential to do work. For both batteries and the atmosphere, this electrical potential is expressed by voltage, which is simply the energy per unit charge. For example, if a battery is rated at 1.5 volts (V), it means that 1.5 joules are available per coulomb of charge (1.5 J/C). A coulomb (C) is equivalent to the charge carried by about 6 × 1019 electrons. The higher the voltage, the greater the energy release for each coulomb transferred.In the case of Earth, a huge voltage difference exists between the surface and the ionosphere—about 400,000 volts! This voltage gradient sets up what we call the fair-weather electric field. The fair-weather field is always present, even in bad weather, so a better name might be the mean electric field. The fair-weather field can be thought of as the background situation on which extreme events such as lightning are superimposed.Does electricity flow in response to the voltage gradient of the fair-weather field? Yes, but because air is a good insulator, the current is weak, about 2000 coulombs per second (2000 Ampere) for the entire planet. In North America, individual houses are typically wired for 200-Ampere service, so we see that the atmospheric current is truly very small. Nevertheless, it does represent a continuous leakage, whereby electrons are transferred from the surface or, equivalently, positive charges are transferred from the atmosphere. This implies that for the mean electric field to be maintained, it must be continuously replenished. As a matter of fact, lightning discharges in thunderstorms are thought to be the primary recharge mechanism. In other words, cloud-to-ground lightning discharges transfer electrons to the surface, maintaining the voltage difference and the resulting electric field.In the lower atmosphere, the fair-weather electric field gradient is on the order of 100 V per meter. (Although this might sound impressive, remember that few ions are present, so the total available energy is very low.) Of course, for lightning to occur, the field strength must be greatly intensified above the background value. How this happens can be only partly explained today, nearly 250 years after Ben Franklin performed his famous kite experiment.What role does cloud-to-ground lightning play in regard to the mean electrical field? Get solution
2. Electricity in the AtmosphereLightning is, of course, an electrical disturbance, much of which can be explained by the basic principles of atmospheric electricity. You know from Chapter 1 that ions (charged particles) are most abundant high in the atmosphere (in the ionosphere, from about 80 to 500 km, or 50 to 300 mi). The upper atmosphere has a positive charge, just as we find near the positive pole of a battery. In the same way that a battery stores energy, electrical charges in the atmosphere represent stored energy and have the potential to do work. For both batteries and the atmosphere, this electrical potential is expressed by voltage, which is simply the energy per unit charge. For example, if a battery is rated at 1.5 volts (V), it means that 1.5 joules are available per coulomb of charge (1.5 J/C). A coulomb (C) is equivalent to the charge carried by about 6 × 1019 electrons. The higher the voltage, the greater the energy release for each coulomb transferred.In the case of Earth, a huge voltage difference exists between the surface and the ionosphere—about 400,000 volts! This voltage gradient sets up what we call the fair-weather electric field. The fair-weather field is always present, even in bad weather, so a better name might be the mean electric field. The fair-weather field can be thought of as the background situation on which extreme events such as lightning are superimposed.Does electricity flow in response to the voltage gradient of the fair-weather field? Yes, but because air is a good insulator, the current is weak, about 2000 coulombs per second (2000 Ampere) for the entire planet. In North America, individual houses are typically wired for 200-Ampere service, so we see that the atmospheric current is truly very small. Nevertheless, it does represent a continuous leakage, whereby electrons are transferred from the surface or, equivalently, positive charges are transferred from the atmosphere. This implies that for the mean electric field to be maintained, it must be continuously replenished. As a matter of fact, lightning discharges in thunderstorms are thought to be the primary recharge mechanism. In other words, cloud-to-ground lightning discharges transfer electrons to the surface, maintaining the voltage difference and the resulting electric field.In the lower atmosphere, the fair-weather electric field gradient is on the order of 100 V per meter. (Although this might sound impressive, remember that few ions are present, so the total available energy is very low.) Of course, for lightning to occur, the field strength must be greatly intensified above the background value. How this happens can be only partly explained today, nearly 250 years after Ben Franklin performed his famous kite experiment.What role does cloud-to-ground lightning play in regard to the mean electrical field? Get solution
