Heat - Not much
The Sun is made of several layers, the "surface layer" is the photosphere.

The photosphere temperature is $5,772 \text{ K}$, not much. Any element less tungsten and rhenium will evaporate, these two will only melt. But in order to heat materials, you need time, and one second isn't much. Just check it:
Your wormhole has a diameter of $d= 100 \text{ m}$ and it's a circle:
$$surface = \pi r^2$$
And $r = \frac{d}{2}$. So:
$$surface = \pi \times \frac{100 \text{m}}{2}^2 = 7,853.98 \text{ m}^2$$
Stars are usually close perfect black bodies, so they emissivity is near $\varepsilon = 1$.
Using the Stefan-Blotzmann law:
$$P = Aj^\text{*} = A \varepsilon \sigma T^4$$
Where:
- $P$ is the total energy emmited in $J/s$ or $W$.
- $A$ is the surface area in $m^2$.
- $j^\text{*}$ is the radiant emittance with dimensions of energy flux (energy per time per are), like $J/s/m^2$ or $W/m^2$.
- $\varepsilon$ is the emisivity.
- $\sigma$ is the Stefan-Botlzmann constant $\sigma = 5.67036713 \times 10^{-8}W \times m^{-2} \times K^{-4}$
- $T$ is the temperature in $K$.
$$P = {7,853.98} \times 1 \times \sigma \times 5,772^4$$
$$P = 494,317,913,890.86 \text{ J/s} = 494 \text{ GJ/s}$$
Your wormhole last one second so $\text{energy} = P * 1 \text{ s} = 494 \text{ GJ/s}$.
Let's melt iron!
It's Enthalpy of vaporization (Also know as heat of vaporization) is $E_v = 340 \text{ kJ/mol}$. It's atomic weight is $A_w = 55.8452$.
You can boil:
$$m = P_v / E_v / A_w$$
$$m = (494,317,913,890.86 \text{ J/s}) / (340,000 \text{ J/mol}) / (55.4852 g/mol)$$
$$m = 26,202.95 \text{ g} = 26.02 \text{ kg}$$
Or melt $645.11 \text{ kg}$ (given the enthalpy of melting is $E_m = 13.84 \text{kJ/mol}$).
Gravity - Deadly but not much
It's surface gravity is $274 \text{ m/s}^2$ (28 times Earth's gravity). You wormhole is at 1 km from Earth's surface but that is negigible ($274.2002 \text{ m/s}^2$ vs $274.1994 \text{ m/s}^2$).
A wormhole of one second will pull all objects to it at $274 \text{ m/s}$. In 28 seconds Earth's gravity will fix it. All people will die due to the impact and all cars, bikes and other stuff will also break due to the impact. The whole Earth's movement will slightly change, it may unstabilize the Earth's orbit after a few millions of years, not sure.
I can't say if buildings are enough strong to not break apart. Gravity is a lot, but it's only a second. Maybe all the structure will crack and destroy.
Particles - Nothing Meaningful
The amount of particles per cubic meter of the photosphere is very low $~10^{23} m^{-3}$, about 0.37% of the particle number per volume of Earth's atmosphere. Also, only 3% of the gas is ionized.
These particles carry a negigible amounts of mass and thus force with them. It's density varies from $1 \times 10^{-3} \text{ kg/m}^3$ to $1 \times 10^{-6} \text{ kg/m}^3$. Even flowing this particles at 7 km/s isn't much (like $7 \text{ N/m}^3$ to $0.007 \text{ N/m}^3$).
The same with temperature. It's composition is 74.9% H and 23.8% He, which is (using the heat capacity) ($5,772 \text{ K} \times (0.749 \times 28.836 \text{ J/(mol*K)} / 1.00784) + (0.238 \times 20.78 \text{ J/(mol*K)} / 4.0026022)) \times 10^{-3} \text{ kg/m}^3 = 273.95 \text{ J/m}^3$ in the worst cases. That amount of energy is very low. It may increase the temperature of air in the surrondings by a few degres, but not much.
Don't worry about it.